Anomalous sulfur isotopes trace volatile pathways in magmatic arcs

Abstract

The cycle of sulfur, an important volatile in Earth9s crust, is the driver of many significant processes such as biological evolution, climate change, and the formation of ore deposits. This study investigates the ancient cycle of volatiles by tracing the indelible signal of anomalous sulfur isotopes, expressed as Δ 33 S ≠ 0, to illuminate the pathway of sulfur recycling through magmatic arcs. We selected the ca. 2.0 Ga Glenburgh gold deposit in the Glenburgh magmatic arc of Western Australia as a natural laboratory for this study. High-precision multiple sulfur isotope analyses of samples from the Glenburgh gold deposit and surrounding granitoid rocks yield the largest known sulfur isotope anomalies (Δ 33 S up to +0.82‰) in rocks <2.33 Ga globally. These data indicate that sulfur, and possibly gold, originated from multiple geochemical reservoirs in sedimentary rocks subducted beneath the magmatic arc, one of which is >2.33 Ga. Multiple sulfur isotope data are able to clarify a process that is cryptic to most other currently available data sets, showing that the cycling of volatiles and metals in arc settings occurs on very large scales, from the atmosphere-hydrosphere through to the lithosphere during crustal generation.